The present invention relates to a wastewater energy recovery unit and more specifically to a household shower wastewater heat recovery unit.
As petroleum-based energy sources dwindle and cost-efficient and renewable energy sources are distant, worldwide consumers are faced with ever-increasing energy costs.
Wasted energy, often in the form of heat escaping from water, is a costly problem. In the U.S., alone, an estimated 120 million homes annually waste an estimated 350 billion kilowatts of energy from hot water running down household drains. With an average cost of $0.07 per kilowatt-hour, this equates to an annual waste of $24.5 billion. For example, the average showering session uses approximately 10 gallons of water. Assuming that half of the 10 gallons used is heated 20-degrees Fahrenheit and that water is mixed with cold water during a typical shower or bath, then to heat that five gallons of water requires three kilowatts of energy. Thus, the three Kilowatts of energy ultimately is lost as water flows out the showerhead.
Latent costs to the environment are not calculated in this loss. Global warming, increased ozone, damage to aquatic life in our streams and rivers, and depleted reserves of fossil fuels are part of this unaccounted loss. More directly, the cost to human health, delicate eco-systems, and lost economic opportunity are impossible to equate in terms of lost energy or money.
Wasted energy drives a huge retrofitting market in the United States. And, the escalating cost associated with energy drives consumer demand for ever-improved devices designed to capture waste energy. To meet this increasing demand, several retailers sell devices designed to manage energy costs. For example, retailers include over 1,200 Lowes home improvement stores, 1,900 Home Depot stores, and 3,500 Walmart stores. Despite the size of this market, existing devices typically are expensive to produce and require costly and complicated installations and otherwise inadequately address the needs of the consumer for a wastewater heat-recovery device.
For example, U.S. Pat. No. 6,016,864 issued to Bae et al and U.S. Pat. No. 5,771,964 also to Bae (The Bae references) describe a heat exchanger with relatively flat fluid conduits. The Bae references incorporate a plurality of relatively flat conduits, an inlet, and an outlet adapted to exchange heat between a fluid inside the conduit and an external fluid. One important limitation: the Bae references feature heat transfer channels with a relatively small hydraulic diameter, preferably in a range of 0.01 inch to 0.20 inch and of short length compared to the supply channels. Specifically, the Bae references attempt to provide the advantages of relatively small hydraulic diameter flow paths without the pressure drops which are usually associated with such relatively small hydraulic diameter flow paths by including supply and drain channels with substantially greater cross-sectional areas than the small flow paths. Moreover, the Bae references teach that the hydraulic fluid within the conduits be isolated from the second fluid. As a result, the Bae references require considerable effort and expense to manufacture and require complicated and costly installation techniques.
U.S. Pat. Nos. 4,398,308 and 4,300,247 both to Berg describes an energy conservation system for a shower. A heat exchanger preheats incoming cold water with hot drain water. This system requires extensive in-the-wall plumbing to affect appropriate heat transfer from the wastewater to the isolated supply line.
Therefore, there remains a need for a wastewater heat recovery unit that over comes the limitations of the prior art and provides solutions to households the world-over. Such a solution must be economical to produce and require no tools to install in the home and require no in-the-wall installation. In addition, the solution should trap heat from shower wastewater as it drains from a person using the shower or directly from the effluent flow from the showerhead. Such a solution should be a “do-it-yourself” project for homeowners, be easy to remove, and easy to service, clean and maintain.